Many materials are known to be porous, generally being naturally porous. The naturally porous materials can be provided as filters or as transpiration coolers for various applications. Nevertheless, many natural materials include porosity that is also substantially “natural”. Simply, the natural porosity of many materials is highly variable. Although porosity for various materials may be within a selected range, the porosity can be unevenly distributed throughout the material. Moreover, the natural porosity of a selected material may be within an extreme of a range rather than within a narrow porosity range.
Nevertheless, it is desirable to provide materials that include a selected porosity. Generally these materials will include a porosity that is substantially consistent throughout the material such that natural variations do not occur within the material or are inconsequential relative to the selected porosity. Therefore, the porosity will include a selected porosity and pore size. The entire material will have known physical characteristics and can be applied in a substantially consistent manner.
Moreover, most often porous materials include a substantially multi-directional porosity. That is, the porosity is distributed such that materials may move through the pores in multiple directions, from a first side to a second side and from the second side to the first side of the material as well as parallel to both sides. If the porous material is provided as a filter or membrane, then a pressure differential across the membrane must be relied upon to move the material in a selected direction. Generally, this requires including additional manufacturing steps or structural elements in the final structure or device.
Therefore, it would be desirable to provide a material that is substantially directionally porous. More specifically, it would be desirable to provide a material having a porosity that allows material to flow along one direction relative to the porous material surfaces. The flow may be dependent upon the material in which the pores are made or the material being flowed across the membrane. Nevertheless, the membrane is substantially uni-directional in its porosity for selected flowable materials.
It is also desired to provide many materials including selected porosities. That is, materials of various types including a selected porosity that includes a selected pore density, selected pore size, and selected directional porosity. Therefore, rather than providing only a single material including a selected porosity with a general technique, the materials could be varied and used in many different applications including different strengths and weight requirements.